1. Field of Invention
The present invention relates to a color reading apparatus using a monochromatic line image sensor.
2. Description of Related Art
As a color reading apparatus is known that uses a monochromatic line image sensor. In such a color reading apparatus, for example, either each of a plurality of light emission diodes of red, green and blue is turned on for a predetermined time in turn or three color filters of red, green and blue are inserted into an optical path between a white light source and a monochromatic line image sensor for a predetermined time in turn while an original to be optically read out (hereinafter referred to as xe2x80x9cread-target originalxe2x80x9d) is fed at a predetermined speed in the direction opposite to the auxiliary scan direction. The reflection light from the read-target original is read (detected) on a line-by-line basis for each color (red, green and blue) by the monochromatic line image sensor.
There may be cases where a reading operation must be temporarily interrupted halfway through a process of reading a sheet of read-target original. For example, when a facsimile transmission or copy is carried out in a facsimile machine or the like, a read-out image signal from the reading apparatus is converted to digital data and subjected to various types of processing. Thereafter, the data thus processed are stored in a buffer memory and then supplied from the buffer memory to a modem or a print apparatus. In this case, if an empty capacity of the buffer memory is reduced, the reading operation must be temporarily interrupted in order to prevent over-flow of the buffer memory.
Therefore, in the case of the conventional color reading apparatus using a monochromatic line image sensor, the empty capacity of the buffer memory is checked for each color (red, green and blue) at the time when the reading operation of one line is finished. When the empty capacity is judged to be less than a predetermined value, a step motor for feeding the read-target original is stopped.
The above described conventional color reading apparatus has a problem that the reading precision is reduced due to the interruption of the reading operation. Thus, a high-quality reproduced image may not be obtained.
The color image data of one line are composed of image data of one line of each color (red, green and blue). It is preferable that the 1-line reading positions for the respective colors are as adjacent to each other as possible. However, when the stepping motor for feeding the read-target original is stopped, some time delay occurs until the read-target original is stopped due to the inertial force of a feeding mechanism. The read-target original is unintentionally fed by some distance during this time delay. Accordingly, when a color reading apparatus is designed so that the reading operation is allowed to be temporarily interrupted at the end time when the reading operation of one line for any color (red, green and blue) is finished. As in the case of the above conventional color reading apparatus, the reading operation may be interrupted, for example, between the reading operation for the red color and the reading operation for the blue color. Thus, the reading position for the red color and the reading position for the blue color are greatly displaced from each other so that an accurate color image data cannot be obtained.
The present invention provides a color reading apparatus which can prevent the reduction in reading precision due to the interruption of the reading operation and a storage medium in which a program for controlling the color reading apparatus is stored.
According to a first aspect of the present invention, there is provided a color reading apparatus in which reflection light from a read-target medium is read on a line-by-line basis for each color of red, green and blue by a monochromatic line image sensor to perform a color reading operation while the relative position between the read-target medium and the monochromatic line image sensor is changed by a feeding apparatus. The color reading apparatus includes a feed control means for stopping a driving source of the feeding apparatus at the time of a 1-line color reading operation which is composed of 1-line reading operations for each of the red, green and blue colors (i.e., 1-line monochromatic reading operations of red, green and blue) in the case where the reading operation for a read-target medium is temporarily interrupted.
According to the above color reading apparatus, when the reading operation for a read-target medium is temporarily interrupted, the feeding control means stops the driving source of the feeding apparatus at the time when a set of 1-line monochromatic reading operations for each of the red, green and blue colors (i.e., the 1-line color reading operation) are completed. Therefore, the reduction in reading precision due to the interruption of the reading operation may be suppressed.
Since the reading operation is not interrupted halfway through the 1-line color reading operation for the red, green and blue colors, the respective 1-line monochromatic image data of the red, green and blue colors which constitute 1-line color image data are necessarily read out at respective reading positions which are mutually adjacent to one another. Thus, a high-precision reading operation an be maintained irrespective of the interruption of the reading operation.
The feeding apparatus may be designed to feed the read-target medium, such as a read-out original or the like, in the opposite direction to the auxiliary scan direction or to feed the light source and the monochromatic line image sensor in the auxiliary scan direction.
The monochromatic line image sensor may be a close contact type, non-contact type image sensor, a CCD image sensor, an MOS type image sensor or the like. The light source for irradiating light to the read-target medium may be light sources for red, green and blue colors, a white light source, or the like. When a white light source is used, three color filters may be inserted into the optical path between the white light source and the monochromatic line image sensor in turn to thereby read a read-target medium for each of the three colors read, green and blue. The order of the reading operations for red, green and blue colors may be arbitrarily set.
A stepping motor may be used as the driving source for the feeding apparatus, however, the driving source is not limited to a stepping motor. Other types of feeding apparatus may be used without departing from the spirit and scope of the present invention.
The feed control means may be implemented by a CPU which operates on the basis of a predetermined program, for example. The feed control means may also be implemented by a microcontroller and peripheral integrated circuit elements, an ASIC or other integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device such as a PLD, PLA, FPGA or PAL, or the like.
According to a second aspect of the present invention, there is provided a color reading apparatus in which the color reading apparatus of the first aspect of the present invention is further provided with red, green and blue light emission diodes serving as an irradiation light source for irradiating light to a read-target medium. A turn-on control device for turning on each of the light emission diodes for a predetermined time in turn is also provided.
According to the above color reading apparatus of the second aspect of the present invention, in addition to the effect of the color reading apparatus of the first aspect, the color reading apparatus can be manufactured at a low price because light emission diodes are used as an irradiation light source. Also, the reading color can be readily and quickly switched to another reading color by use of the light emission diodes.
The number of the red, green and blue light emission diodes may be set to any value. Further, the respective red, green and blue light emission diodes may be packaged into one body. The turn-on control means may be implemented by a CPU operating on the basis of a predetermined program, a microcontroller and peripheral integrated circuit elements, an ASIC or other integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device such as a PLD, PLA, FPGA or PAL, or the like.
According to a third aspect of the present invention, there is provided a storage medium for storing a program to read reflection light from a read-target medium on a line-by-line basis for each color of red, green and blue by a monochromatic line image sensor to perform a color reading operation. The program contains a feed control program for stopping a driving source of a feeding apparatus at the time when a set of 1-line monochromatic reading operations for red, green and blue colors are completed in the case where a reading operation of a read-target medium is temporarily interrupted.
According to the storage medium of the third aspect of the present invention, a CPU of a communication device is operated on the basis of the program thus stored. Thereby, the color reading apparatus of the present invention is implemented.
A ROM may be used as the storage medium. The present invention is not limited to the ROM, however, and an EEPROM, CD-ROM, hard disk, floppy disk, magnetic tape, and the like may be used.